Subterranean (including subsea) cased and open well bores are conventionally known and widely used for a variety of purposes, including but not limited to geothermal well bores or well bores that provide access to liquid or gaseous hydrocarbons or other deposits. Packers are conventionally known and are widely used in well bores to provide zonal isolation, well sealing, general mandrel to wall sealing and other applications.
Packers generally include an elongated elastomeric packer element that may be carried on a mandrel. The packer element has a first or reduced diameter configuration in which the outer peripheral surface of the packer element is spaced from the well bore wall to permit positioning of the packer element and mandrel in the well bore. The packer element also has a second or enlarged diameter configuration in which the outer peripheral surface of the packer element seals against the well bore wall and between the well bore wall and the mandrel.
Packer elements may be non-swellable or swellable. Non-swellable packer elements may be changed from their first configuration to their second configuration by an external force such as a fluid pressure acting on the interior of the packer element or axial forces that longitudinally compress the packer element and cause it to expand radially so that the outer peripheral surface of the packer element seals against the well bore wall. Swellable packer elements are changed from their first configuration to their second configuration by exposure of the material of the packer element to a swelling fluid after the mandrel and swellable packer element are positioned in the well bore. Once the non-swellable or swellable packer element has changed to its enlarged diameter configuration, the packer element seals between the mandrel and the cased or open well bore wall to provide a high pressure and high temperature seal.
In the use of well bore packer elements, the sealing pressure of the packer element against the well bore wall and the axial length of the packer element are significant factors in determining the sealing characteristics of the packer element. Longitudinally longer packer elements may increase the sealing characteristics by increasing the sealing area, but longer packer elements can be more difficult to produce, ship and maneuver down a well bore. Increased sealing pressure of the packer element against the well bore wall created by swelling may increase the sealing characteristics, but increased sealing pressure can tend to cause axial extrusion of the packer element. To reduce the tendency of axial extrusion, various packer anti-extrusion backup systems have been proposed in U.S. Pat. Nos. 7,661,471 and 7,806,193.